The number of obese children in the US has increased dramatically over the past thirty years. Most efforts to reverse this trend, however, have not been effective. Two factors may underlie their limited success. First, most programs do not take into account children's personal risk for obesity, including their genetic and prenatal risks. Second, there is little information about factors that predict weight trajectories during childhood. The proposed study tests a comprehensive developmental model of obesity that incorporates child-based (genetic, prenatal) and family-based (parenting practices and modeling) risk factors for obesity, and seeks to identify constellations of risk that predict unhealthy vs. healthy weight trajectories. Furthermore, the degree to which the postnatal environment mediates, mitigates or amplifies the expression of child-based risks for obesity is examined. As such, this study represents a first step in developing new prevention programs that can consider children's weight trajectories in light of their unique vulnerabilities and needs. The proposed research is an extension of the ongoing Early Growth and Development study (EGDS). EGDS is a prospective, longitudinal study of adoptive children, along with their birth parents and adoptive families. Because adoptive children's postnatal environments are distinct from their prenatal environments and genetic risk, the unique and interactive contributions of genes, prenatal, and postnatal factors to child development can be clarified in adoption studies. EGDS has focused on the origins of child emotional and behavioral problems and competence. This proposal seeks to extend the scope of EGDS to include childhood obesity EGDS is comprised of two participant cohorts, for a total sample of 561 sets of adopted children, and their birth and adoptive parents. Cohort I includes 361 sets (birth dates between January 2003 - January 2006; R01-HD042608, PI Leve), and Cohort II includes 200 sets (birth dates between May 2007 and May 2009; R01- DA020585, PI Neiderhiser). EGDS has been funded to assess Cohort I children and adoptive families from child age 9 months through 8 years, and Cohort II children and adoptive families from child age 9 months to 6 years (R01-MH92118, PIs Leve, Neiderhiser). Birth parents from both Cohorts have also been assessed on an ongoing basis since 3 months post-partum. The specific aims of the proposed extension of EGDS are to: (1) Identify genetic, prenatal, and postnatal environmental predictors of weight trajectories from 2-9 years of age; and (2) Test postnatal environmental mediation and moderation models for children's weight trajectories. The proposed research will use growth and prenatal data collected during previous assessments, and gather new data related to children's growth, and behavioral, genetic and postnatal family risks for obesity when children are between 7 and 9 years of age. Analyses will combine data from both Cohorts. This research will enhance understanding of the contributions of genetic, prenatal and postnatal risks to weight trajectories, and of postnatal environments that are most likely to foster healthy weights in the presence of genetic or prenatal risk.